Isaacs' syndrome associated with myasthenia gravis, showing remission after cytoreductive surgery of pleural recurrence of thymoma

Systematic Review of the Clinical Characteristics and Management of Isaac Syndrome

OBJECTIVES

Isaac syndrome (IS) is a condition characterized by peripheral nerve hyperexcitability caused by voltage-gated potassium channel (VGKC)-complex antibodies. Muscle twitching, stiffness, hypertrophy, and dysautonomic characteristics, such as hyperhidrosis, are common manifestations. The syndrome can be autoimmune or paraneoplastic, with thymoma being a common cause of paraneoplastic IS. Furthermore, this condition could be handed down from one generation to another. However, there is limited information regarding outcomes, relapses, associated syndromes, associated malignancies (other than thymoma), and treatment options. Despite its rarity, there remains a need for effective management strategies for patients with IS. To address this gap, we conducted a systematic review to summarize the most common and effective treatments of IS in immunomodulatory agents and symptomatic medications, as well as to describe outcomes, relapses, and associated malignancies. Altogether, this review serves to guide clinical practice recommendations for IS and highlight areas for further research.

METHODS

We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol to conduct a systematic review of cases reposted through the PubMed and Google Scholar databases. The terms "Isaac Syndrome" and "Acquired Neuromyotonia" were used. The Joanna Briggs Institute's critical appraisal tool was used to evaluate the quality of the included studies.

RESULTS

We identified 61 case reports and 4 case series, comprising a total of 70 patients with IS (mean age at onset: 42.5 ± 18 years, and 69% were males). Fourteen cases reported relapses. Thymoma was the most common malignancy associated with IS, followed by lymphoma. Among various serum antibodies, voltage-gated potassium channel-complex antibodies were the most reported antibodies elevated in IS (reported in 38 patients and elevated in 21 patients [55.2%]), followed by acetylcholine ganglionic receptor antibodies, which were reported in 30% of patients (n = 21) and were elevated in 5 cases. The most common electromyography findings were myokymic discharges (n = 22), followed by fasciculations (n = 21) and neuromyotonia (n = 19). For treatment, combining anticonvulsants such as carbamazepine with immunotherapy therapy showed the best results in controlling the symptoms. Among immunotherapy therapies, the combination of plasma exchange plus intravenous high-dose steroids achieved the best results in the acute treatment of IS ([n = 6], with improvement noted in 83.3% [n = 5] of cases). Among the symptomatic treatments with anticonvulsants, carbamazepine was the most efficacious anticonvulsant in treatment of IS, with an average effective dosing of 480 mg/day (carbamazepine was used in 32.3% of acute treatment strategies [n = 23], with improvement noted in 73.9% [n = 17] of cases).

CONCLUSIONS

IS a rare neuromuscular syndrome that tends to affect middle-aged men. These patients should be screened for thymoma and other malignancies such as lymphomas. The management of IS symptoms can be challenging, but based on our review, the combination of multiple immunosuppressives such as IV steroids and plasmapheresis with anticonvulsants such as carbamazepine seems to achieve the best results.

Autoimmune neuromyotonia

PURPOSE OF REVIEW

Autoimmune neuromyotonia encompasses a group of rare immune-mediated neurological disorders frequently associated with anti-contactin-associated protein-like 2 (CASPR2) antibodies and featuring clinical and electrical signs of peripheral nerve hyperexcitability (PNH). We aim to summarize the current knowledge on immune-mediated neuromyotonia, focusing on clinical presentations, pathophysiology, and management.

RECENT FINDINGS

Neuromyotonia is a major feature of several autoimmune neurological syndromes characterized by PNH with or without central neurological system involvement. Experimental and clinical evidence suggest that anti-CASPR2 antibodies are directly pathogenic in autoimmune neuromyotonia patients.

SUMMARY

Neuromyotonia, a form of PNH, is a major feature in several syndromes associated with anti-CASPR2 antibodies, including cramp-fasciculation syndrome, Isaacs syndrome, Morvan syndrome, and autoimmune limbic encephalitis. Diagnosis relies on the identification of motor, sensory, and autonomic signs of PNH along with other neurological symptoms, anti-CASPR2 antibody-positivity, and of characteristic electroneuromyographic abnormalities. Paraneoplastic associations with thymoma are possible, especially in Morvan syndrome. Patients usually respond to immune-active treatments, including steroids, intravenous immunoglobulins, plasma exchanges, and rituximab.

Isaacs' syndrome as the initial presentation of malignant thymoma and associated with double-positive voltage-gated potassium channel complex antibodies, a case report

BACKGROUND

Isaacs' syndrome is a peripheral nerve hyperexcitability (PNH) syndrome due to peripheral motor nerve instability. Acquired Isaacs' syndrome is recognized as a paraneoplastic autoimmune disease with possible pathogenic voltage-gated potassium channel (VGKC) complex antibodies. However, the longitudinal correlation between clinical symptoms, VGKC antibodies level, and drug response is still unclear.

CASE PRESENTATION

A 45-year-old man had progressive four limbs soreness, muscle twitching, cramps, and pain 4 months before admission. Electromyography (EMG) studies showed myokymic discharges, neuromyotonia, and an incremental response in the high-rate (50 Hz) repetitive nerve stimulation (RNS) test. Isaacs' syndrome was diagnosed based on clinical presentations and EMG reports. Serum studies showed positive VGKC complex antibodies, including leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (CASPR2) antibodies. The acetylcholine receptor antibody was negative. Whole-body computed tomography (CT) and positron emission tomography revealed a mediastinal tumor with the great vessels encasement, right pleura, and diaphragm seeding. Biopsy confirmed a World Health Organization type B2 thymoma, with Masaoka stage IVa. His symptoms gradually improved and both LGI1 and CASPR2 antibodies titer became undetectable after concurrent chemoradiotherapy (CCRT) and high dose steroid treatment. However, his Isaacs' syndrome recurred after the steroid was reduced 5 months later. Follow-up chest CT showed probable thymoma progression. LGI1 antibody turned positive again while CASPR2 antibody remained undetectable.

CONCLUSIONS

Our patient demonstrates that Isaacs' syndrome could be the initial and only neuromuscular manifestation of malignant thymoma. His Isaacs' syndrome is correlated well with the LGI1 antibody level. With an unresectable thymoma, long-term immunosuppressant therapy may be necessary for the management of Isaacs' syndrome in addition to CCRT for thymoma.

Afterdischarges in Myasthenia Gravis

Introduction: This study aimed to analyze the clinical features of myasthenia gravis (MG) in combination with the afterdischarges and compare the characteristics of afterdischarges in MG with different serum antibodies. Methods: Ninety-two patients with MG were analyzed retrospectively. The afterdischarges were investigated using motor nerve conduction examination, F-wave examination, and repetitive nerve stimulation (RNS). Results: Afterdischarges were observed after the M wave in 14 of 92 patients. Three of these 14 patients tested positive for the muscle-specific tyrosine kinase antibody (MuSK-Ab), and 11 patients tested positive for the acetylcholine receptor antibody (AchR-Ab). The characteristics of the afterdischarges on RNS differed distinctly between the two antibody groups. The afterdischarges occurred on the first stimulation, but decreased on the second and subsequent stimulations in patients with MuSK-MG, while the afterdischarges continued to occur on each stimulation in patients with AchR-MG. Discussion: The characteristics of the afterdischarges on RNS enabled easy identification of their synaptic or neurogenic nature.

Muscle-Specific Tyrosine Kinase Antibody Positive Myasthenia Gravis With Peripheral Nerve Hyperexcitability: Case Report and Literature Review

OBJECTIVES

Administration of acetylcholinesterase inhibitors can bring about peripheral nerve hyperexcitability symptom in muscle-specific tyrosine kinase antibody positive myasthenia gravis, but the changes in electromyography before and after drug withdrawal have not been described in detail.

METHODS

Electromyography was performed on a case of muscle-specific tyrosine kinase antibody positive myasthenia gravis with peripheral nerve hyperexcitability correlated with the administration of pyridostigmine bromide before and after drug withdrawal, respectively.

RESULTS

Afterdischarges close after M waves appeared on the tibial nerve, common peroneal nerve, median nerve, and ulnar nerve, and these presented unique characteristics in repetitive nerve stimulation. Ten days after pyridostigmine bromide withdrawal, the second electromyography examination was carried out and showed that the afterdischarges on all nerves disappeared dramatically and the amplitude of tibial nerve F waves was elevated than before.

CONCLUSIONS

Afterdischarges can be an important indicator of muscle-specific tyrosine kinase antibody positive myasthenia gravis with peripheral nerve hyperexcitability correlated with acetylcholinesterase inhibitors.

A systematic review of paraneoplastic syndromes associated with thymoma: Treatment modalities, recurrence, and outcomes in resected cases

OBJECTIVE

Paraneoplastic syndromes associated with thymomas remain incompletely understood. The objective was to examine the association between surgically resected thymomas and paraneoplastic syndromes over the past half century.

METHODS

A primary PubMed/MEDLINE search was used to identify published articles describing paraneoplastic syndromes associated with thymomas from 1960 to 2019. A secondary search identified additional articles referenced in the articles found in the primary search. Kaplan-Meier and log-rank test were used for time-to-event data analyses.

RESULTS

From 407 articles describing 507 patients, 123 different paraneoplastic syndromes were associated with thymoma. The 5 most common paraneoplastic syndromes were myasthenia gravis, pure red cell aplasia, lichen planus, Good syndrome, and limbic encephalitis. Complete or partial resolution of paraneoplastic syndrome symptoms after surgery was noted in 76% of patients, of whom 21% had a relapse or new paraneoplastic syndrome onset after surgery. The most common adjunctive therapy associated with resolution of paraneoplastic syndrome was corticosteroids (30%). For all patients after surgery, thymoma recurrence was observed in 17% of cases, whereas recurrence of paraneoplastic syndrome was observed in 34% of cases, and both were observed in approximately 11% of cases. The 5- and 10-year overall survivals were 78% and 66%, respectively. Improved overall survival was associated with patients who had total resolution from paraneoplastic syndrome.

CONCLUSIONS

A comprehensive assessment of publications over the past half century suggests that a multimodal treatment approach that includes surgical resection of thymomas is able to achieve paraneoplastic syndrome resolution in a majority of patients. Onset of new paraneoplastic syndromes after surgery is associated with the recurrence of the first paraneoplastic syndrome, and resolution of paraneoplastic syndrome is associated with improved overall survival.

Paraneoplastic disorders in thymoma patients

Thymic malignancy is often associated with paraneoplastic neurological diseases (PNDs) and recognition of these disorders is important for physicians who treat these patients. The most common thymoma-associated PNDs are myasthenia gravis (MG), acquired neuromyotonia (Isaacs' syndrome), encephalitis, Morvan's syndrome, and myositis. Diagnosis of these disorders is complex but often aided by testing for specific autoantibodies, including those to the acetylcholine receptor for MG and to contactin-associated protein-like 2, protein of the voltage-gated potassium channel complex, in patients with acquired neuromyotonia, Morvan's syndrome, or encephalitis. Patients who manifest these disorders should be screened for thymoma at diagnosis, and worsening of these PNDs may be associated with recurrent thymoma. These disorders can cause profound disability but usually respond to immunotherapy, and often improve with thymoma treatment. Close cooperation among a team of specialists is required to take proper care of these patients.

[Myasthenia, from the internist's point of view]

Myasthenia gravis is an autoimmune disease due to specific antibodies inducing a neuromuscular transmission defect causing muscle fatigability. If onset of the disease may be at any age, myasthenia gravis concerns mostly young adults, in majority females. The disease characteristic features are the following: ocular symptoms (ptosis or diplopia) as main initial manifestation, extension to other muscles in 80 % of the cases, variability of the deficit, effort induced worsening, successive periods of exacerbation during the disease course, severity depending on respiratory and swallowing impairment (if rapid worsening, a myasthenic crisis is to be suspected), association with thymoma in 20 % of patients and with other various autoimmune diseases, most commonly hyperthyroidism and Hashimoto's disease. Diagnosis relies on the clinical features, improvement with cholinesterase inhibitors, detection of specific autoantibodies (anti-AChR or anti-MuSK), and significant decrement evidenced by electrophysiological tests. The points concerning specifically the internist have been highlighted in this article: diagnostic traps, associated autoimmune diseases, including inflammatory myopathies that may mimic myasthenia gravis, adverse effects of medications commonly used in internal medicine, some of them inducing myasthenic syndromes. The treatment is well codified: the treatment is well codified: (1) respect of adverse drugs contra-indications, systematically use of cholinesterase inhibitors, (2) thymectomy if thymoma completed with radiotherapy if malignant, (3) corticosteroids or immunosuppressive agent in severe or disabling form, (4) intensive care unit monitoring, plasmapheresis or intravenous immunoglobulins for patients with myasthenic crisis.

Cytoreductive surgery combined with hyperthermic intrapleural chemotherapy to treat thymoma or thymic carcinoma with pleural dissemination

BACKGROUND

The treatment of thymoma or thymic carcinoma with pleural dissemination remains controversial due to the unpredictable natural history of this tumor. Our study discusses the combination of cytoreductive surgery with hyperthermic intrapleural chemotherapy to treat thymoma or thymic carcinoma with pleural dissemination.

METHODS

From February 2008 to January 2010, there were four patients with pleural thymoma metastases undergoing cytoreductive surgery and intrathoracic hyperthermic perfusion with chemotherapy at our department. After video-assisted thoracoscopic surgery, the hyperthermic perfusion system was set up for hyperthermic intrapleural chemotherapy. The thoracic cavity was perfused at a speed of approximately 1.8-2.3 L/min with 0.9% normal saline. The intrathoracic temperature remained between 42°C and 43°C. The perfusion process lasted for 2 hours.

RESULTS

There were no perioperative deaths. During the hyperthermic perfusion, the patient's core temperature varied from 36.3°C and 39.3°C and pulse varied from 59 beats/min and 126 beats/min. Intraoperative sinus tachycardia occurred in two elderly patients. No hematologic toxicity and nephrotoxicity was observed within 1 week after surgery. Postoperative pneumonia occurred in one elderly patient. Patients were followed up for 1-4 years. One elderly patient died of heart failure 1 year after surgery. There were no patients with local recurrence or metastases to distant sites.

CONCLUSIONS

Cytoreductive surgery and intrathoracic hyperthermic perfusion with chemotherapy may be effective in treating thymoma or thymic carcinoma with pleural dissemination and has an encouraging impact on the patients' long-term survival.